UO<sub>2-<i>x</i></sub>燃料芯块的晶粒生长动力学

UO_2-x燃料芯块的晶粒生长动力学

摘要: 本文采用恒速升温和等温烧结实验方法研究了亚化学计量UO_2-x燃料芯块的晶粒生长动力学。结果表明，以UO_2+x+5%U为原料，可得到密度为94.91%TD～96.23%TD（TD为理论密度）、O与U的原子个数比为1.975～1.990的合格的亚化学计量UO_2-x燃料芯块；在烧结温度≤1 650 ℃时晶粒生长速率较低，在烧结温度≥1750 ℃时晶粒生长速率较高；初始晶粒尺寸G₀不能忽略不计，亚化学计量UO₂-x燃料芯块的晶粒生长动力学符合4次方模型G⁴-G⁴₀=k₀texp(-1 000Q/RT)，晶粒生长速率常数k₀=78.76 μm⁴/h，激活能Q=433.35 kJ/mol。

Abstract: Grain growth kinetics of the substoichiometric UO_2-xfuel pellets were studied with constant heating speed and isothermal sintering experiments. Substoichiometric UO2-x fuel pellets can be fabricated with qualified density of 94.91%TD-96.23%TD (TD is theory density) and O and U atomic ratio of 1.975-1.990 when the mixed powders of UO_2+x and 5%U are sintered. Grain growth rate is very low when sintering temperature is below 1 650 ℃, but higher above 1750 ℃. It is found that the starting grain size G₀ cannot be neglected and the grain growth kinetics equation of the substoichiometric UO2-x fuel pellets is G⁴-G⁴₀=k0texp(-1 000Q/RT), resulting in grain growth feature exponent n=4, rate constant k0=78.76 μm4/h and activation energy Q=433.35 kJ/mol.